Improved ductile tungsten filament incandescent lamps were introduced in 1911 by General Electric Company. Their original efficiency was approximately 10 lumens (a unit of light measurement) per watt. Between 1911 and 1936 a new coiled coil design and the use of gas filling increased the efficiency to 17 lumens per watt for a 100 watt bulb. In the coiled coil filament, wire is formed into a coil about three inches long and then that is coiled; thus, the term "coiled coil" wire. It has long been recognized that the efficiency of an incandescent lamp can be improved substantially. The tungsten filament emits a smaller amount of the energy as visible light. Over 80% is in the infrared and ultraviolet (nonvisible) spectrum.
Since the 1930's, there have been many approaches to the development of an improved tungsten filament that has longer life and higher efficiency. Those developments that have accomplished these goals have been much more expensive than the standard tungsten lamp.
Bell Telephone Laboratories has produced a microscopic texturing of the tungsten surface which greatly enhances the emissivity. However, the microscopic texturing is expected to deteriorate during the operation of a filament at the typical filament temperature of 2675.degree. C.